Method of coating a substrate with nanoparticles including a metal oxide

ABSTRACT

One exemplary embodiment may include a method comprising: depositing a solution comprising an organometallic compound on a substrate, drying the solution to provide a film of the organometallic compound and at least partially oxidizing an organic component of the organometallic compound to provide nanoparticles including metal oxides on the substrate which would have multiuse industrial applications.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 12/335,650 filed Dec. 16, 2008 and claims the benefit of thefiling date thereof.

TECHNICAL FIELD

The field to which the disclosure generally relates to includes methodsof making coatings including nanoparticles, and products includingnanoparticles including a layer including organometallic nanoparticlesor nanoparticles including a metal oxide.

BACKGROUND

Fuel cells produce energy through the electrochemical reaction betweenhydrogen and oxygen/air with water as an end product. Inside the fuelcells, water can accumulate inside reacting gas distribution channelsformed in fuel cell bipolar plates, thereby reducing the mass transportof the reactant gases through the channels and to the catalyst layerwhere the electrical chemical reaction occurs. Furthermore, theaccumulation of water on a variety of other substrates may also beundesirable. In addition, nanoparticles including metal oxides may havea variety of applications.

SUMMARY OF EXEMPLARY EMBODIMENTS OF THE INVENTION

One exemplary embodiment includes forming a liquid coating on asubstrate, the liquid coating including a reactive organometalliccompound dissolved in a non-polar solvent, drying the liquid coating toprovide a film including the organometallic compound and oxidizing(decomposing).

Other exemplary embodiments of the invention will become apparent fromthe detailed description provided hereinafter. It should be understoodthat the detailed description and specific examples, while disclosingexemplary embodiments of the invention, are intended for purposes ofillustration only and are not intended to limit the scope of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention will become more fully understoodfrom the detailed description and the accompanying drawings, wherein:

FIG. 1A illustrates a product and a method of making the same, includingdepositing a solution including an organometallic compound on asubstrate according to one exemplary embodiment.

FIG. 1B illustrates a product and a method of making the same, includingdrying the solution deposited on the substrate of FIG. 1 to form a filmof organic metallic material on the substrate according to one exemplaryembodiment.

FIG. 1C illustrates a product and a method of making the same, includingoxidizing (decomposing) the film on the substrate of FIG. 1B to form alayer including nanoparticles including a metal oxide according to oneexemplary embodiment.

FIG. 2 illustrates a product and a method of making the same including afuel cell bipolar plate having a layer including nanoparticles includinga metal oxide selectively deposited thereon according to one exemplaryembodiment.

FIG. 3 illustrates an alternative embodiment of a fuel cell bipolarplate including a layer including nanoparticles including a metal oxideselectively deposited thereon according to one exemplary embodiment.

FIG. 4 illustrates another embodiment of a fuel cell bipolar plateincluding a low contact resistant coating deposited over a surface ofthe bipolar plate and a layer including nanoparticles including a metaloxide selectively deposited over portions of the low contact resistantlayer according to one exemplary embodiment.

FIG. 5 illustrates a fuel cell bipolar plate including a low contactresistant material selectively deposited on lands of a fuel cell bipolarplate and a layer including nanoparticles including a metal oxideselectively deposited in the channels of the bipolar plate according toone exemplary embodiment.

FIG. 6 is a sectional view of a portion of a fuel cell stack including alayer including nanoparticles including a metal oxide deposited overportions of one or more of fuel components in the fuel cell stackaccording to one exemplary embodiment.

FIG. 7 illustrates a product including a layer including nanoparticlesincluding a metal oxide formed on a surface thereof according to oneexemplary embodiment of the invention.

FIG. 8 illustrates a sectional view of a housing having a layerincluding nanoparticles including a metal oxide deposited on a surfaceof the housing according to one exemplary embodiment.

FIG. 9 illustrates a plurality of metal oxide particles or rods formedby coating a porous filter paper with an organometallic compound drying,and oxidizing (decomposing) the same and burning off the filter paperaccording to one exemplary embodiment.

FIG. 10 illustrates a plurality of metal oxide nanoparticle rods formedby depositing a solution including an organometallic compound over a matformed of random carbon fibers, drying the solution and oxidizing theresultant film and burning off the carbon mat to form the nanoparticlerods or any desired morphology depending on the template according toone exemplary embodiment.

FIG. 11 illustrates an FE-SEM of titanium oxide nanoparticles preparedby a method according to one embodiment.

FIG. 12 illustrates another FE-SEM of titanium oxide nanoparticlesprepared by a method according to one embodiment.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following description of the embodiment(s) is merely exemplary(illustrative) in nature and is in no way intended to limit theinvention, its application, or uses.

One exemplary embodiment of the invention includes oxidizing a materialincluding an organometallic compound to provide nanoparticles includinga metal oxide. In one embodiment, substantially all of the organiccontent of the organometallic compound is oxidized/decomposed leavingsubstantially only metal oxides. The organometallic compound may bedeposited on a substrate as a solution, the solution dried to provide afilm including the organometallic compound and thereafter the filmincluding the organometallic compound is oxidized to providenanoparticles including the metal oxide that strongly adhere to thesubstrate. The nanoparticles including a metal oxide may have a varietyof applications. Such applications may include, but are not limited to,depositing the nanoparticles on, in or through a substrate to imparthydrophilic properties thereto, or the nanoparticles including metaloxides may be utilized as a high surface area and electrochemicallystable catalyst support or as a hydrogen storage and hydrogen producingmaterial. In one embodiment, the metal oxide may have the formulaM_(X)O_(a), where both x and a are greater than 0 and less than 10. Themetal component (M) may be a single element or multiple elements. Forexample, in another embodiment, the metal oxides may have the formulaM1_(x)M2_(y)M3_(z)O_(a), where both x and a are greater than 0 and lessthan 10, and both y and z are less than or equal to 0 and less 10.

To provide hydrophilic properties and to serve as a catalyst support,the metal component of the metal oxide may include, but is not limitedto, titanium, tantalum, zirconium or niobium. For hydrogen storage, themetal component of the now particle metal oxides may include, but is notlimited to, at least one of titanium, tantalum, or zirconium. Hydrogenmay be stored on high surface area materials produced by the process andmay include nanoparticles consisting essentially of metal oxides or theorganic component of the organometallic compound may only be partiallyoxidized, leaving a plurality of metallic oxides linked together byorganic struts. The current invention can be used to make materials forhydrogen production utilizing the semiconductor properties of the highsurface area nanocrystalline metal oxide. When light with a well definedwavelength is illuminated on the metal oxide, electrons from the valanceband of the semiconductor oxide move from the valance band to theconduction band leaving behind positive holes which are known to bestrong oxidizing agents that can be used to oxidize organicpollutants/waste. The free electrons can then be trapped on anotherelectrode to evolve hydrogen. Thus the current materials might be usedfor making hydrogen while cleaning the environment from organicwaste/pollutants.

Referring now to FIG. 1A, one embodiment of the invention includesdepositing an organometallic solution 14 on a substrate 12. The solutionincludes an organo metallic compound in a solvent which may include, butis not limited to, a non polar solvent. Thereafter, as shown in FIG. 1B,the solution 14 may be dried to provide a layer or film of theorganometallic compound 16. The organometallic compound may be a singlematerial or a variety of organometallic materials may be includedwherein the organic component and/or the metallic component varies. Asshown in FIG. 1C, the film or layer of organometallic compound 16 maythen be oxidized/decomposed, for example, but not limited to, exposingthe film to air to provide a layer of film including nanoparticlesincluding a metallic oxide 18. If necessary or desired, additionaloxidizing processes may be utilized to completely or partially oxidizethe organic component or the metal component of the organometalliccompound.

Referring now to FIG. 2, one exemplary embodiment includes providing asubstrate 12 which may be a fuel cell bipolar plate which may be asingle piece or may include a first piece 12 a and a second piece 12 bjoined together. Each of the first piece 12 a and second piece 12 b mayinclude a first face 20 having defined therein a reactant gas flow fieldincluding a plurality of lands 22 and channels 24 through which thereactant gases flow. A second face 26 may have defined therein at leasta portion of a cooling channel 28 for flowing cooling fluid therethrough to cool the fuel cell. In one exemplary embodiment, a maskmaterial 21 may be deposited on the lands, leaving the channels exposed.The organometallic solution 14 may be deposited or formed over the mask21 and into the channels 24 as shown on piece 12 a. The solution 14 maybe formed or deposited or applied by dipping the bipolar plate in asolution of the bath, spraying, rolling or other suitable technique.After the solution 14 has been dried and/or oxidized, the mask 21 may bemoved including the film or nanoparticles attached thereto leave a layeror film of nanoparticles including metal oxides deposited only in thechannels 24. Although masking will ensure that the freshly preparedtitanium oxide nanoparticles do not cover the lands and interfere withcontact resistance, it is possible that the nanoparticles can be appliedusing nozzles that only apply the reactive organometallic only insidethe channels which will decompose into the nanoparticles inside thechannels leaving the lands intact

Referring now to FIG. 3, another exemplary embodiment includes a fuelcell bipolar plate 12 including a first piece 12 a and second piece 12 bformed by stamping metal substrates, such as stainless steel.

Referring now to FIG. 4, a low contact resistant material 30 such as,but not limited to, gold may be deposited over a portion or all of thefirst face 20, including on the lands 22 and into the surfaces formingthe channel 24. The layer including nanoparticles including metal oxides18, may be deposited over the low contact resistant material 30, butpreferably only on the surfaces defining the channel 24.

Referring now to FIG. 5, another exemplary embodiment includes a fuelcell bipolar plate 12 including a low contact resistant material 30 suchas, but not limited to, gold, deposited only on the lands 22 with thelayer including nanoparticles including metal oxides 18 deposited onlyon the surfaces forming the channels 24.

FIG. 6 is a sectional view of a portion of a fuel cell stack including amembrane, which may be a proton exchange membrane 38 having a firstphase 37 and an opposite second phase 39. A first catalyst 36 may bedeposited on the first face 37 of the membrane 38 and a second catalyst40 may be deposited on the second membrane face 39. A layer includingnanoparticles including metal oxides 18 may be deposited on any of thefuel cell components completely covering a surface or selectivelydeposited thereon, or in or through various fuel cell components. Forexample, a layer including nanoparticles including metal oxides 18 maybe deposited on one or both of the catalyst layers 36, 40.Alternatively, the layer including nanoparticles including metal oxides18 may be deposited on either diffusion media layer 32, 34, or on eithermicroporous layer 34, 42 if present on the gas diffusion media layers32, 34. The first gas diffusion media layer 32 may include a first face31 and an opposite second face 33. Similarly, the second gas diffusionmedia layer 44 may include a first face 43 and an opposite second face45. The layer including nanoparticles including metal oxides 18 may bedeposited directly on the second face 33, 45 of the first gas diffusionmedia layer 32 or second gas diffusion media layer 44 respectively. Yetin another embodiment, the layer 18 may be deposited on the first face30 adjacent the bipolar plate 12 a, or on the first face 43 adjacent thesecond bipolar plate portion 12 b. In one embodiment, the layerincluding nanoparticles including metal oxides 18 may be deposited in amanner generally aligned with the channels 24 formed in the bipolarplate portions 12 a, 12 b. In yet another exemplary embodiment, thenanoparticles including metal oxides 18′ may be deposited through atleast portions of the body of the gas diffusion media layers 32, 44, forexample, in an area underlying the channels 24 formed in the bipolarplate 12 a, 12 b.

Referring now to FIG. 7, in yet another exemplary embodiment, the layerincluding nanoparticles including metal oxides 18 may be deposited on asubstrate 12 such as a glass substrate, which may be a vehicle window orwindshield.

Referring now to FIG. 8, in yet another exemplary embodiment, the layerincluding nanoparticles including metal oxides 18 may be deposited on asurface of a housing substrate 12, such as, but not limited to, avehicle headlamp or taillight housing cover to provide hydrophilicproperties to the surface thereof and reduce condensation of waterdroplets. The hydrophilic nature of the nanocrystalline metal oxide maybe further enhanced when illuminated by the housing light. The lightproduces positive holes inside the oxide that could potentially oxidizemost organic contaminants render the surface of the housing less proneto air contamination.

Referring now to FIG. 9, a plurality of nanoparticles rods may beprovided and may be utilized for a variety of applications, including,but not limited to, catalysts or hydrogen storage. The rods 18 may beformed in one embodiment by depositing an organometallic solution on aporous fibrous mat which may be woven. The mat may be made from asacrificial material such as carbon which may be burnt off, etched orotherwise removed to leave the plurality of metal oxide rods 18.Similarly, as shown in FIG. 10, the plurality of rods 18 may be providedin a random form using a mat with unwoven, randomly positioned fibers,depositing the organometallic solution, drying the same and oxidizingthe same. The carbon mat may be burnt off to provide the plurality ofnanoparticle rods 18.

In another embodiment the solution is deposited in the pores of a porousmaterial, dried and oxidized, and thereafter the porous material isremoved to leave nanoparticles in the shape of the pores.

FIGS. 11-12 are FE-SEM photomicrographs of titanium oxide nanoparticlesprepared according to one embodiment of the invention.

In one exemplary embodiment of the invention, a reactive titaniumorganometallic compound is dissolved in a non-polar solvent low boilingpoint to provide a solution that may include 0.1-2 weight percent of theorganometallic compound. In one embodiment, nanoparticles were preparedfrom one weight percent titanium isopropoxide in n-hexane. Othersolvents may include, but are not limited to, n-heptane, xylene, orethyl acetate. The weight percent of the organic metallic compoundincluded in the solution may range from 0.1-5, 0.1-2, 0.1-1 weightpercent or ranges there between.

Referring again to FIG. 6, the following is a description ofnon-limiting exemplary embodiment of various fuel cell components on, inor through which the layer including nanoparticles including metaloxides may be deposited.

Microporous Layer

In one embodiment, the microporous layer may be made from materials suchas carbon blacks and hydrophobic constituents such aspolytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), andmay have a thickness ranging from about 2 to about 100 micrometers. Inone embodiment the microporous layer may include a plurality ofparticles, for example including graphitized carbon, and a binder. Inone embodiment the binder may include a hydrophobic polymer such as, butnot limited to, polyvinylidene fluoride (PVDF), fluoroethylene propylene(FEP), polytetrafluoroethylene (PTFE), or other organic or inorganichydrophobic materials. The particles and binder may be included in aliquid phase which may be, for example, a mixture of an organic solventand water to provide dispersion. In various embodiments, the solvent mayinclude at least one of 2-propanol, 1-propanol or ethanol, etc. Thedispersion may be applied to a fuel cell substrate, such as, a gasdiffusion media layer or a hydrophobic coating over the gas diffusionmedia layer. In another embodiment, the dispersion may be applied to anelectrode. The dispersion may be dried (by evaporating the solvent) andthe resulting dried microporous layer may include 60-90 weight percentparticles and 10-40 weight percent binder. In various other embodiments,the binder may range from 10-30 weight percent of the dried microporouslayer.

Gas Diffusion Media Layer

In one embodiment of the invention, the gas diffusion media layer mayinclude any electrically conductive porous material. In variousembodiments, the gas diffusion media layer may include non-woven carbonfiber paper or woven carbon cloth which may be treated with ahydrophobic material, such as, but not limited to, polymers ofpolyvinylidene fluoride (PVDF), fluroethylene propylene, orpolytetrafluoroethylene (PTFE). The gas diffusion media layer may havean average pore size ranging from 5-40 micrometers. The gas diffusionmedia layer may have a thickness ranging from about 100 to about 500micrometers.

Electrode Layers

In one embodiment, the electrodes (cathode layer and anode layer) may becatalyst layers which may include catalyst particles such as platinum,and an ion conductive material such as a proton conducting ionomer,intermingled with the particles. The proton conductive material may bean ionomer such as a perfluorinated sulfonic acid polymer. The catalystmaterials may include metals such as platinum, palladium, and mixturesof metals such as platinum and molybdenum, platinum and cobalt, platinumand ruthenium, platinum and nickel, platinum and tin, other platinumtransition-metal alloys, and other fuel cell electrocatalysts known inthe art. The catalyst materials may be finely divided if desired. Thecatalyst materials may be unsupported or supported on a variety ofmaterials such as but not limited to finely divided carbon particles.

Membrane

A variety of different types of membranes may be used in embodiments ofthe invention. The solid polymer electrolyte membrane useful in variousembodiments of the invention may be an ion-conductive material. Examplesof suitable membranes are disclosed in U.S. Pat. Nos. 4,272,353 and3,134,689. Such membranes are also known as ion exchange resinmembranes. The resins include ionic groups in their polymeric structure;one ionic component for which is fixed or retained by the polymericmatrix and at least one other ionic component being a mobile replaceableion electrostatically associated with the fixed component. The abilityof the mobile ion to be replaced under appropriate conditions with otherions imparts ion exchange characteristics to these materials.

The ion exchange resins can be prepared by polymerizing a mixture ofingredients, one of which contains an ionic constituent. One broad classof cationic exchange, proton conductive resins is the so-called sulfonicacid cationic exchange resin. In the sulfonic acid membranes, thecationic exchange groups are sulfonic acid groups which are attached tothe polymer backbone.

The formation of these ion exchange resins into membranes or chutes iswell-known to those skilled in the art. The preferred type isperfluorinated sulfonic acid polymer electrolyte in which the entiremembrane structure has ionic exchange characteristics. These membranesare commercially available, and a typical example of a commercialsulfonic perfluorocarbon proton conductive membrane is sold by E. I.DuPont D Nemours & Company under the trade designation NAFION. Othersuch membranes are available from Asahi Glass and Asahi ChemicalCompany. The use of other types of membranes, such as, but not limitedto, perfluorinated cation-exchange membranes, hydrocarbon basedcation-exchange membranes as well as anion-exchange membranes are alsowithin the scope of the invention.

Bipolar Plates

In one embodiment of the invention, the bipolar plates may include oneor more layers of a metal for electrically conductive compositematerial. In one embodiment, the bipolar plates include stainless steel.The lands and channels may be formed in the bipolar plate by machining,etching, stamping, molding or the like. The lands and channels maydefine a reactant gas flow field to deliver a fuel on one side of thebipolar plate and an oxidant on the other side of the plate.

In one embodiment the nanoparticles, which may be in the form of rodsmay be used as catalyst support for electrodes. The electrochemicalstability along with the high surface area of the nanoparticles that byfar exceeds those of the currently used carbon blacks that are known tohave stability issues such as carbon corrosion.

One embodiment may include depositing a solution comprising anorganometallic compound on a substrate to provide a film of theorganometallic compound and at least partially oxidizing an organiccomponent of the organometallic compound to provide nanoparticles;coating a catalyst on the nanoparticles to provide catalyst coatednanoparticles; forming a fuel cell electrode using the catalyst coatednanoparticles. In another embodiment a solution including the catalystcoated nanoparticles may be deposited on one of a fuel cell membrane,fuel cell microporous layer, or fuel cell diffusion media layer.Alternatively the solution including the catalyst coated nanoparticlesmay be deposited on a decal and dried to form an electrode. Theelectrode may be applied to one of a fuel cell membrane, fuel cellmicroporous layer, or fuel cell diffusion media layer.

Another embodiment may include a process including making fuel cellmembranes including adding an organometallic solution including anorganometallic compound to a polyelectrolyte, such as Nafion, solutionto provide a mixture and casting the mixture so that the metallic oxideparticles, such as titanium oxide, are attached to the polyelectrolyteto produce a self humidification membrane. The organic component of theorganometallic compound may be oxidized before or during the casting toprovide metallic oxide particles attached to the polyelectrolyte polymerof the polyelectrolyte solution. The hydrophilicity of titania will tendto retain water in the membrane and thus reducing or eliminating theneed for external humidification of the membrane.

The above description of embodiments of the invention is merelyexemplary in nature and, thus, variations thereof are not to be regardedas a departure from the spirit and scope of the invention.

What is claimed is:
 1. A process comprising: adding an organometallic solution comprising metallic oxide particles to a polyelectrolyte solution to provide a mixture, and wherein the polyelectrolyte solution comprises a polyelectrolyte; casting the mixture so that the metallic oxide particles are attached to the polyelectrolyte to produce a self humidifying membrane.
 2. A process as set forth in claim 1 wherein the metallic oxide particles comprise titanium isopropoxide.
 3. A process as set forth in claim 1 wherein the polyelectrolyte solution includes a solvent comprising n-hexane.
 4. A process as set forth in claim 2 wherein the titanium isopropoxide is present in about 1 weight percent.
 5. A process as set forth in claim 1 wherein the organometallic solution is present in about 0.1 to about 5 weight percent.
 6. A process as set forth in claim 1 wherein the organometallic solution is present in about 0.1 to about 2 weight percent.
 7. A process method as set forth in claim 1 wherein the organometallic solution is present in about 0.1 to about 1 weight percent.
 8. A process as set forth in claim 1 wherein the organometallic solution is partially oxidized so that a plurality of said metallic oxide particles are linked together by organic struts.
 9. A process comprising: adding an organometallic solution comprising titanium isopropoxide particles to a polyelectrolyte solution comprising a solvent comprising n-hexane to provide a mixture; casting the mixture so that the titanium isopropoxide particles are attached to the polyelectrolyte solution to produce a self-humidifying membrane.
 10. A process comprising: adding an organometallic solution comprising an organometallic compound to a polyelectrolyte solution to provide a mixture, and wherein the polyelectrolyte solution comprises a polyelectrolyte; casting the mixture and oxidizing the organometallic compound during the casting to produce metallic oxide particles and so that the metallic oxide particles are attached to the polyelectrolyte to produce a self humidifying membrane. 